EDITORIAL article Front. Mar. Sci., 27 December 2022Sec. Deep-Sea Environments and Ecology Volume 9 - 2022 | https://doi.org/10.3389/fmars.2022.1098359

Deep-sea mining may be just a few years away and yet society is struggling to assess the positive aspects, such as increasing the supply of metals for battery production to fuel the green revolution, versus the potentially large environmental impacts. Mining of polymetallic (manganese) nodules from the deep ocean is likely to be the first mineral resource targeted and will involve direct impacts to hundreds of km2 of seabed per mine per year. However, the mining activity will also cause the generation of large sediment plumes that will spread away from the mine site and have both immediate and long-term effects over much wider areas. We discuss what the impacts of plumes generated near the seabed by mining vehicles may be and how they might be measured in such challenging environments. Several different mining vehicles are under development around the world and depending on their design some may create larger plumes than others. We discuss how these vehicles could be compared so that better engineering designs could be selected and to encourage innovation in dealing with plume generation and spread. These considerations will aid the International Seabed Authority (ISA) that has the task of regulating mining activities in much of the deep sea in its commitment to promote the Best Available Technology (BAT) and Best Environmental Practice (BEP).

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Intense turbidity currents occur in the Malaylay Submarine Canyon off the northern coast of Mindoro Island in the Philippines. They start in very shallow waters at the shelf break and reach deeper waters where a gas pipeline is located. The pipeline was displaced by a turbidity current in 2006 and its rock berm damaged by another 10 years later. Here we propose that they are triggered near the mouth of the Malaylay and Baco rivers by direct sediment resuspension in the shallow shelf and transport to the canyon heads by typhoon-induced waves and currents. We show these rivers are unlikely to generate hyperpycnal flows and trigger turbidity currents by themselves. Characteristic signatures of turbidity currents, in the form of bed shear stress obtained by numerical simulations, match observed erosion/deposition and rock berm damage patterns recorded by repeat bathymetric surveys before and after typhoon Nock-ten in December 2016. Our analysis predicts a larger turbidity current triggered by typhoon Durian in 2006; and reveals the reason for the lack of any significant turbidity current associated with typhoon Melor in December 2015. Key factors to assess turbidity current initiation are typhoon proximity, strength, and synchronicity of typhoon induced waves and currents. Using data from a 66-year hindcast we estimate a ~8-year return period of typhoons with capacity to trigger large turbidity currents.

Ecological risk assessment for deep-sea mining is challenging, given the data-poor state of knowledge of deep-sea ecosystem structure, process, and vulnerability. Polling and a scale-intensity-consequence approach (SICA) were used in an expert elicitation survey to rank risk sources and perceived vulnerabilities of habitats associated with seabed nodule, sulfide, and crust mineral resources. Experts identified benthic habitats associated with seabed minerals as most vulnerable to habitat removal with a high degree of certainty. Resource-associated benthic and pelagic habitats were also perceived to be at risk from plumes generated during mining activities, although there was not always consensus regarding vulnerabilities to specific risk sources from different types of plumes. Even for risk sources where habitat vulnerability measures were low, high uncertainties suggest that these risks may not yet be dismissed. Survey outcomes also underscore the need for risk assessment to progress from expert opinion with low certainty to data-rich and ecosystem-relevant scientific research assessments to yield much higher certainty. This would allow for design and deployment of effective precautionary and mitigation efforts in advance of commercial exploitation, and adaptive management strategies would allow for regulatory and guideline modifications in response to new knowledge and greater certainty.

This paper reviews key aspects of the implementation of the Convention on Biological Diversity's Ecologically or Biologically Significant Area (EBSA) process to date, anticipating global marine coverage of that process in so far as is possible by the end of 2018. EBSAs merge marine and coastal physical, biological and biogeographical information held by States, diverse scientific institutions and individual experts to identify inherent value of marine biodiversity, as well as providing a focus for either States or international organisations with sectoral competences to apply potential management measures to protect and sustainably manage biodiversity. In assessing information made available at dedicated EBSA Regional Workshops, several common patterns emerged, both in the data made available and in the gaps in information. The latter include missing information, representation of taxa and features of interest, and specialist expertise. The review exercise detailed here has highlighted the value and efficacy of the EBSA process and the information it has generated, despite some recognised shortcomings. It further suggests that there is potential to strengthen the EBSA portfolio by (i) adding some selected new areas yet to be described, (ii) revisiting existing EBSAs to add both new and existing information, and (iii) reconsidering some areas previously deemed to not meet the EBSA criteria by incorporating both new and existing information. Improving the systematic assessment of areas against the EBSA criteria could be achieved using a combination of (i) spatially precise systematic conservation approaches, supported by (ii) predictive modelling and biogeographic multi-criteria approaches based on expert judgement.

Mineral exploitation has spread from land to shallow coastal waters and is now planned for the offshore, deep seabed. Large seafloor areas are being approved for exploration for seafloor mineral deposits, creating an urgent need for regional environmental management plans. Networks of areas where mining and mining impacts are prohibited are key elements of these plans. We adapt marine reserve design principles to the distinctive biophysical environment of mid-ocean ridges, offer a framework for design and evaluation of these networks to support conservation of benthic ecosystems on mid-ocean ridges, and introduce projected climate-induced changes in the deep sea to the evaluation of reserve design. We enumerate a suite of metrics to measure network performance against conservation targets and network design criteria promulgated by the Convention on Biological Diversity. We apply these metrics to network scenarios on the northern and equatorial Mid-Atlantic Ridge, where contractors are exploring for seafloor massive sulfide (SMS) deposits. A latitudinally distributed network of areas performs well at (i) capturing ecologically important areas and 30 to 50% of the spreading ridge areas, (ii) replicating representative areas, (iii) maintaining along-ridge population connectivity, and (iv) protecting areas potentially less affected by climate-related changes. Critically, the network design is adaptive, allowing for refinement based on new knowledge and the location of mining sites, provided that design principles and conservation targets are maintained. This framework can be applied along the global mid-ocean ridge system as a precautionary measure to protect biodiversity and ecosystem function from impacts of SMS mining.

Biodiversity loss from deep-sea miningThe Tu'i Malila vent field in the Lau Basin, southwest Pacific.Lau Basin foundation species (Alviniconcha spp.snails, Ifremeria nautilei snails, and Bathymodiolus septemdierum mussels) live in diffuse flow on the surfaces

Recent years have seen an upsurge in interest in mining in the world’s deep oceans, in areas beyond national jurisdiction. Such mining activity has the potential to cause environmental impacts over large areas. As contractors plan to move from exploration to exploitation activities it is important to develop guidance to ensure that these activities are managed in a way that is as environmentally sustainable as possible. This paper presents the outcomes of an international workshop on environmental management for deep-sea mining (DSM). The workshop presented protocols for environmental management, which were tested using a comprehensive polymetallic nodule mining scenario developed with industry input. The workshop started by presenting a framework for environmental management of deep-sea mining, which introduced the use of a conceptual model as a method of storing and updating environmental data and the synthesis of that data throughout the project. The second session focused on the incorporation of the precautionary approach and adaptive management into the framework. Two discussion sessions were held to discuss Environmental Impact Assessment (EIA) in the context of the scenario: the first considered scoping and screening EIAs, while the second reviewed the full EIA assessment. Subsequent discussion focussed on environmental management at the regional scale. This concentrated on the Regional Environmental Assessment (REA) - including its purpose, the scale and scope, and practicalities - and the assignment of protected areas as an approach for regional environmental management. Use of a scenario as a basis for the evaluation of protocols on the environmental management of DSM was novel amongst workshops, facilitating focussed discussion despite the high uncertainty surrounding DSM activities. The results of these discussions are summarised in the paper.

This chapter contains sections titled: Introduction Regional Setting Methods Results and Discussion Summary

Sediments in deep water basins often include turbidites that record sediment input from adjacent continental margins. In seismically active areas, where turbidity currents are triggered by earthquakes, the basinal turbidite sequence may thus contain a record of palaeoseismicity, which can be used to infer the frequency of earthquakes affecting the margins of the basin. This is particularly useful where large earthquakes have a recurrence interval than is greater than the historical record. However, turbidity currents can be triggered by several processes, and it is often difficult to trace individual turbidites to their precise source areas and to assign a definite trigger to a particular turbidite. Here, we demonstrate that turbidites emplaced at similar to 6600 and similar to 8300 Cal yr BP in the Tagus Abyssal Plain, off Portugal, correlate with erosional hiatuses in two submarine canyons on the continental margin. The turbidites are sourced from simultaneous landsliding in both canyons, requiring regional triggers interpreted as earthquakes. An earthquake recurrence interval for the continental margin of similar to 4000 years is estimated by extrapolation to deeper turbidites in the basin sequence. However, the example of the 1755 earthquake, which caused widespread devastation in southwest Iberia, shows that palaeoseismic interpretations must be made with caution. The 1755 earthquake had a magnitude >8.5 and yet the associated turbidite in the abyssal plain is typically similar to 5 cm thick, while older turbidites can be >1 m thick. Given the large 1755 earthquake magnitude, the difference in turbidite thickness is unlikely to be related to the relative size of triggering earthquakes. Instead, we suggest that the offshore location of the 1755 earthquake, coupled with low sedimentation rates during the Holocene, may have limited the size of the associated turbidite.

Carlo Heip*, Manuel Barange, Roberto Danovaro, Marion Gehlen, Anthony Grehan, Filip Meysman, Temel Oguz, Vangelis Papathanassiou, Katja Philippart, Jun She , PaulTréguer, Rachel Warren, Paul Wassmann, Phil Weaver, Rita Yu, Justus van Beusekom, Philip Boyd, Andrew Cooper, Hein J.W. de Baar, Henk de Haas, Felix Janssen, Wolfgang Ludwig, LeifToudal Pedersen, Michael Tsimplis, Hans Von Storch, Jan Bart Calewaert and Niall McDonough